CHK1 inhibition as a strategy for targeting fanconi anemia (FA) DNA repair pathway deficient tumors

<p>Abstract</p> <p>Background</p> <p>DNA repair deficient tumor cells have been shown to accumulate high levels of DNA damage. Consequently, these cells become hyper-dependent on DNA damage response pathways, including the CHK1-kinase-mediated response. These observations suggest that DNA repair deficient tumors should exhibit increased sensitivity to CHK1 inhibition. Here we offer experimental evidence in support of this hypothesis.</p> <p>Results</p> <p>Using isogenic pairs of cell lines differing only in the Fanconi Anemia (FA) DNA repair pathway, we showed that FA deficient cell lines were hypersensitive to <it>CHK1 </it>silencing by independent siRNAs as well as CHK1 pharmacologic inhibition by Gö6976 and UCN-01. In parallel, an siRNA screen designed to identify gene silencings synthetically lethal with CHK1 inhibition identified genes required for FA pathway function. To confirm these findings <it>in vivo</it>, we demonstrated that whole zebrafish embryos, depleted for <it>FANCD2 </it>by a morpholino approach, were hypersensitive to Gö6976. Silencing of FA genes led to hyper-activation of CHK1 and vice versa. Furthermore, inactivation of CHK1 in FA deficient cell lines caused increased accumulation of DNA strand and chromosomal breakages. These results suggest that the functions subserved by CHK1 and the FA pathway mutually compensate in maintaining genome integrity. As CHK1 inhibition has been under clinical trial in combination with cisplatin, we showed that the FA specific tumoricidal effect of CHK1 inhibition and cisplatin was synergistic.</p> <p>Conclusion</p> <p>Taken together, these results suggest CHK1 inhibition as a strategy for targeting FA deficient tumors.</p

Adaptive Evolution and the Birth of CTCF Binding Sites in the <i>Drosophila</i> Genome

Changes in the physical interaction between cis-regulatory DNA sequences and proteins drive the evolution of gene expression. However, it has proven difficult to accurately quantify evolutionary rates of such binding change or to estimate the relative effects of selection and drift in shaping the binding evolution. Here we examine the genome-wide binding of CTCF in four species of Drosophila separated by between ∼2.5 and 25 million years. CTCF is a highly conserved protein known to be associated with insulator sequences in the genomes of human and Drosophila. Although the binding preference for CTCF is highly conserved, we find that CTCF binding itself is highly evolutionarily dynamic and has adaptively evolved. Between species, binding divergence increased linearly with evolutionary distance, and CTCF binding profiles are diverging rapidly at the rate of 2.22% per million years (Myr). At least 89 new CTCF binding sites have originated in the Drosophila melanogaster genome since the most recent common ancestor with Drosophila simulans. Comparing these data to genome sequence data from 37 different strains of Drosophila melanogaster, we detected signatures of selection in both newly gained and evolutionarily conserved binding sites. Newly evolved CTCF binding sites show a significantly stronger signature for positive selection than older sites. Comparative gene expression profiling revealed that expression divergence of genes adjacent to CTCF binding site is significantly associated with the gain and loss of CTCF binding. Further, the birth of new genes is associated with the birth of new CTCF binding sites. Our data indicate that binding of Drosophila CTCF protein has evolved under natural selection, and CTCF binding evolution has shaped both the evolution of gene expression and genome evolution during the birth of new genes.</p

Gyroless Spin-Stabilization Controller and Deorbiting Algorithm for CubeSats

CubeSats are becoming increasingly popular in the scientific community. While they provide a whole new range of opportunities for space exploration, they also come with their own challenges. One of the main concerns is the negative impact which they can have in the space debris problem. Commonly lacking from attitude determination and propulsion capabilities, it has been difficult to provide CubeSats with means for active deorbiting. While electric propulsion technology has been emerging for its application in CubeSats, little or no literature is available on methods to enable it to be used for deorbiting purposes, especially within the tight constraints faced by these nanosatellites. We present a new and simple algorithm for CubeSat deorbiting, which proposes the use of novel electric propulsion technology with minimum sensing and actuation capabilities. The algorithm is divided into two stages: a spin-stabilization control; and a deorbiting-phase detection. The spin-stabilization control is inspired by the B-dot controller. It does not require gyroscopes, but only requires magnetometers and magnetorquers as sensors and actuators, respectively. The deorbiting-phase detection is activated once the satellite is spin-stabilized. The algorithm can be easily implementable as it does not require any attitude information other than the orbital information, e.g., from the Global Positioning System receiver, which could be easily installed in CubeSats. The effectiveness of each part of the algorithms is validated through numerical simulations. The proposed algorithms outperform the existing approaches such as deorbiting sails, inflatable structures, and electrodynamic tethers in terms of deorbiting times. Stability and robustness analysis are also provided. The proposed algorithm is ready to be implemented with minimal effort and provides a robust solution to the space junk mitigation efforts

Genome-Wide DNA Methylation Profiles Reveal Common Epigenetic Patterns of Interferon-Related Genes in Multiple Autoimmune Diseases

Graves’ disease (GD), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) are complex autoimmune diseases sharing common clinical, genetic and pathogenetic features. However, the commonalities of the DNA methylation profiles for these diseases are still unknown. We conducted an integrative analysis of the multiple-autoimmune disease methylation dataset including GD, RA, SLE, and SSc samples, to identify the common methylation patterns of autoimmune diseases. We identified 15,289 differentially methylated sites between multiple-autoimmune disease patients and controls in CD4+ T cells. We found that the most significant differentially methylated sites had a remarkable enrichment in type I interferon (IFN) pathway genes. Similarly, we identified 9,295 differentially methylated sites between GD/SSc patients and controls in CD8+ T cells. The overall IFN-related gene panel annotated by gene ontology (GO) showed an excellent diagnostic capacity in CD4+ T cells (Sensitivity = 0.82, specificity = 0.82 and AUC = 0.90), while IFI44L, another IFN-related gene not annotated by GO, showed high prediction ability in both CD4+ (AUC = 0.86) and CD8+ (AUC = 0.75) T cells. In conclusion, our study demonstrated that hypomethylation of IFN-related genes is a common feature of GD/RA/SLE/SSc patients in CD4+ T cells, and the DNA methylation profile of IFN-related genes could be promising biomarkers for the diagnosis of GD, RA, SLE, and SSc

Managerial ability, compensation incentives, and corporate performance

Enterprise managers play a decisive role in management decisions. With the emergence of managerial ability measurement methods, the influence of managerial ability on enterprise development has received wide attention. Taking Chinese A-share listed companies from 2007 to 2019 as samples, this paper uses a fixed-effect model to examine the impact of management abilities on corporate performance and studies the moderating effect of compensation incentives on this impact. It is found that managerial ability has a significant positive correlation with the performance of listed companies, and this positive correlation is more obvious when the management has higher compensation incentives. Further research shows that higher ability management helps improve the performance of firms with low financing constraints but has no significant effect on the performance of firms with high financing constraints. In addition, compared with state-owned enterprises, the managerial ability of non-state-owned enterprises can promote the improvement of enterprise performance. This paper studies the impact of managerial ability on firm performance from the perspective of compensation incentives, enriching the related literature on managerial ability and firm performance

Genome editing with Cas9 in adult mice corrects a disease mutation and phenotype

We demonstrate CRISPR-Cas9–mediated correction of a Fah mutation in hepatocytes in a mouse model of the human disease hereditary tyrosinemia. Delivery of components of the CRISPR-Cas9 system by hydrodynamic injection resulted in initial expression of the wild-type Fah protein in ~1/250 liver cells. Expansion of Fah-positive hepatocytes rescued the body weight loss phenotype. Our study indicates that CRISPR-Cas9–mediated genome editing is possible in adult animals and has potential for correction of human genetic diseases.National Cancer Institute (U.S.) (Grant 2-PO1-CA42063)National Cancer Institute (U.S.) (Core Grant P30-CA14051)National Institutes of Health (U.S.) (Grant R01-CA133404)David H. Koch Institute for Integrative Cancer Research at MIT (Marie D. and Pierre Casimir-Lambert Fund)National Institutes of Health (U.S.) (Centers for Cancer Nanotechnology Excellence 5-U54-CA151884-04)MIT-Harvard Center of Cancer Nanotechnology ExcellenceNational Institutes of Health (U.S.) (1K99CA169512

Global microRNA depletion suppresses tumor angiogenesis

MicroRNAs delicately regulate the balance of angiogenesis. Here we show that depletion of all microRNAs suppresses tumor angiogenesis. We generated microRNA-deficient tumors by knocking out Dicer1. These tumors are highly hypoxic but poorly vascularized, suggestive of deficient angiogenesis signaling. Expression profiling revealed that angiogenesis genes were significantly down-regulated as a result of the microRNA deficiency. Factor inhibiting hypoxia-inducible factor 1 (HIF-1), FIH1, is derepressed under these conditions and suppresses HIF transcription. Knocking out FIH1 using CRISPR/Cas9-mediated genome engineering reversed the phenotypes of microRNA-deficient cells in HIF transcriptional activity, VEGF production, tumor hypoxia, and tumor angiogenesis. Using multiplexed CRISPR/Cas9, we deleted regions in FIH1 3′ untranslated regions (UTRs) that contain microRNA-binding sites, which derepresses FIH1 protein and represses hypoxia response. These data suggest that microRNAs promote tumor responses to hypoxia and angiogenesis by repressing FIH1.Swedish Research CouncilHoward Hughes Medical Institute (International Student Research Fellowship)National Institutes of Health (U.S.) (grant number R01-CA133404)MIT-Harvard Center of Cancer Nanotechnology Excellence (grant no. U54-CA151884)David H. Koch Institute for Integrative Cancer Research at MIT (Marie D. and Pierre Casimir-Lambert Fund)National Cancer Institute (U.S.) (Koch Institute Support (core) Grant P30-CA14051))National Institutes of Health (U.S.) (grant EB016101-01A1)Damon Runyon Cancer Research Foundation (Research Fellow (DRG-2117-12)